How the poll was conducted

The Associated Press-GfK Poll on the midterm elections was conducted by GfK Roper Public Affairs & Corporate Communications Oct. 13-18. It is based on landline and cell phone telephone interviews with a nationally representative random sample of 1,501 adults, which included 846 likely voters. Interviews were conducted with 1,051 respondents on landline telephones and 450 on cellular phones.

Digits in the phone numbers dialed were generated randomly to reach households with unlisted and listed landline and cell phone numbers.

Interviews were done both in English and Spanish.

As is done routinely in surveys, results were weighted, or adjusted, to ensure that responses accurately reflect the population's makeup by factors such as age, sex, education, and race. In addition, the weighting took into account patterns of phone use _ landline only, cell only and both types _ by region.

No more than one time in 20 should chance variations in the sample cause the results to vary by more than plus or minus 3.3 percentage points from the answers that would be obtained if all adults in the U.S. were polled. The margin of error for likely voters is plus or minus 4.4 percentage points.

There are other sources of potential error in polls, including the wording and order of questions.